The present invention relates to an art of conveyance, more particularly to an art of effectively conveying a base plates.
A printed circuit board for an electronic machine such as a computer has an electrically insulating base plate provided with a wiring pattern on at least one side of the base plate. The wiring pattern is made of a copper film, for example. The printed circuit board is manufactured in a process described from now on. The electrically insulating base plate is first supplied from a base plate feeder to the first-stage portion of a base plate conveyance passage on a base plate conveyor. The base plate is coated with the copper film nearly all over the plate in advance. The conveyor conveys the base plate to a laminator which is an automatic thin film sticking apparatus by which a resist film, which is a photosensitive resin film, and a cover film, which is a light-transmissible resin film for protecting the resist film, are automatically stuck to the surface of the copper film on the base plate. The base plate conveyor thereafter conveys the base plate to a resist film exposure appliance which functions so that a latent image of the wiring pattern is made in the resist film stuck to the base plate. The conveyor then conveys the base plate to an automatic thin film peeling appliance by which the cover film laminated of the resist film on the base plate is automatically peeled therefrom. The conveyor then conveys the base plate to a resist film developing appliance which develops the latent image in the resist film so that a mask is created. The conveyor thereafter conveys the base plate to an etching appliance which partly etches the copper film through the mask so that the wiring pattern is made of the unetched portions of the copper film. After that, the base plate is subjected to various plating steps and an electrically insulating film providing step so that the printed circuit board is completed. At the last-stage portion of the base plate conveyance passage, the base plate conveyor conveys the printed circuit board to a printed circuit board receiver so that the board is housed therein, thus finishing the process of manufacturing the board.
It is ideal that the plural processing appliances are sequentially disposed along the base plate conveyance passage on the base plate conveyor to make the consistent process of the manufacturing of the printed circuit board. However, since each of the processing appliances is large in size and occupation area, the process of manufacturing of the printed circuit board is usually made inconsistent and divided into a plurality of portions in reality. In other words, the base plate conveyor is usually divided into a plurality of portions, along the base plate conveyance passages on which the processing appliances are disposed. The divided portions of the conveyor are built in the processing appliances or connected as external units thereto. The base plate feeder for supplying the electrically insulating base plate is disposed at the base plate conveyance passage on the first-stage portion of the divided conveyor. The printed circuit board receiver for receiving the printed circuit board is disposed at the base plate conveyance passage on the last-stage portion of the divided conveyor. In each of the base plate feeder and the base plate receiver, a plurality of electrically insulating base plates or printed circuit boards are piled together in such a manner that the reverse side of one base plate, on which the wiring pattern is made, is put in contact with the obverse side of another base plate. For that reason, very high load acts to the obverse side of the lowermost of the piled base plates so that the resist film of the wiring pattern on the lowermost base plate is likely to be damaged due to pressure of even a minute mutual displacement between the base plate in the piling thereof. This is a problem.
It is conceivable that a housing rack system, in which the electrically insulating base plates or the printed circuit boards are housed in a leant state in grooves provided at prescribed intervals in a housing rack, is adopted for each of the base plate feeder and the printed circuit board receiver in order to solve the problem. However, since one edge of each of the base plates is put in the groove of the housing rack in the housing rack system, the base plate buckles too much to be housed in the groove if the thickness of the base plate is small. This is another problem.
Since the completed circuit board housed in the printed circuit board receiver needs to be transferred therefrom to a printed circuit board feeder provided at the first-stage portion of another divided process, it is not only time-consuming to transfer the board to the feeder but also the resist film or/and wiring pattern of the board is likely to be damaged. This is yet another problem.